Combined developer and fixer



2,7s2,120 COMBINED nnvnLoPER AND FIXER Jerome Stewart Goldhammer, Levittown, and John Andrew Maurer, 512, New York, N. Y.

No Drawing. Application February 15, 1954, Serial No. 410,426

14 Claims. or. 96-61 This invention relates to chemical compositions for combined developing and fixing of silver halide photographic emulsions.

Previously described combined developing and fixing baths can be divided into two general classes. The first of these is characterized by high concentrations of reducing and fixing agents and by high alkalinity, the baths having a pH of 11.0 or higher. The second class is characterized by much lower concentrations of reducing and fixing agents and lower alkalinity, with pH values of 9.5 or lower.

Typical modern formulas of the first class are those of Keelan, given in Photographic Engineering, vol. 4, No. 3, formulas 315 and 34S. Formula 315 has pH of 11.55, and is used, with brush agitation, for 3 minutes at 75 F. in a tray. Formula 348 has pH 11.35; it is used for 10 minutes at 68 F. in a deep tank.

Further examples of the first class of combined developing and fixing baths of the prior art are Examples 1 and 2 of U. S. Patent 2,230,977 (Garnet P. Ham). These formulas have pH values of 11.0 and 11.2. They are used for times of the order of 10 minutes at 65 de grees F.

Developing and fixing baths of this first class have the advantage of comparatively high activity; that is, they operate rapidly and at the same time produce images of desirably high density and high contrast, but this property is not obtained without a number of disadvantages. Because they are highly alkaline, the baths cause irritation and cracking of the skin of anyone working with them, unless rubber gloves are worn. The high alkalinity also causes softening and swelling of the gelatine emulsion, giving rise to reticulation, frilling, susceptibility to scratches, and poor dimensional stability of the image. After treatment in such a bath, the swollen gelatine holds a greater quantity of all the chemical substances present than after conventional separate developing and fixing. For this reason, and also because the swollen condition or" the gelatine retards diffusion, it is necessary to wash the film or plate for a longer time than usual to insure permanence. After washing, a longer time is needed to dry the swollen gelatine. These losses of time in washing and drying are great enough to offset the time saving achieved by combining the operations of developing and fixing.

The images produced by these concentrated and highly alkaline baths have substantially higher chemical fog and coarser grain than those produced by conventional separate developing and fixing baths compounded to produce similar gainmas under like conditions of time and temperature.

Combined developing and fixing baths of this class also have a righ rate of aerial oxidation; therefore, when continuoumy exposed to the air, as they are when employed in deep tank processing, they soon lose activity.

It has been recognized for a long time that combining the operations of developing and fixing should make control of time and temperature much less important itedStates Patent 2,782,120 Patented Feb. 19, 1957 than it is when using separate developing and fixing baths. in the case of a conventional developer with separate fixation it is well known that an increase of either time or temperature results in an increase of density, and usually also of contrast, in the image, up to the point at which the maximum attainable density is reached in the areas of "reatest exposure. After this point is reached the contrast diminishes as density continues to increase in the areas of less exposure. in a combined developing and fixing bath, density and contrast undergo no change with prolonged immersion, because after fixation is complete no further development can take place. The effects of temperature changes are minimized because the effects of the change of developing rate with change of temperature are largely, though not entirely, counteracted by a similar change of fixing rate.

This advantage of relative insensitivity to changes of time and temperature in processing is not available in the practical use of the first or active class of combined developing and fixing baths of the prior art. Because of the high alkalinity of these baths, any substantial increase of the time of immersion, or elevation of the temperature above that for which the formula has been designed, leads to reticulation, frilling of the edges of the emulsion, and severe dimensional changes. These effects limit the usable time and temperature ranges so severely that they are not much wider than the ranges that are practical with separate developing and fixing baths.

Combined developing and fixing baths of the second class in the prior art effectively avoid the above disadvantages, but they accomplish this result at the expense of extremely long processing time, commonly 20 minutes to an hour. For example, the bath disclosed as Example 3 in U. S. Patent 2,230,977 (Ham), which has pH of 9.6, is stated to process panchromatic film in 25 minutes at 65 degrees F. When the action is as slow as this there is not much advantage in combined developing and fixing, since equivalent results can be obtained in less time by conventional separate developing and fixing baths. Also, because these baths of the second class of the prior art are very dilute, they are rapidly exhausted. Some compositions of this class are exhausted by a single use.

Because of the disadvantages stated above, no combined developing and fixing bath of either class in the prior art has ever come into extensive practical use.

The present invention overcomes all of these disadvantages of the combined developing and fixing baths of the prior art. It provides solutions of moderate alkalinity, having pH values of 9.5 or lower, which compare favorably in activity with previous formulas having pH values of 11.0 or higher. These new solutions do not cause skin irritation. They are highly stable; in resistance to aerial oxidation and in constancy of results when used repeatedly they compare well with the best conventional separate developing and fixing formulas. They also compare well with these conventional separate formulas in useful life, as measured by the area of photographic materal that can be processed in a given volume of solution before the bath ceases to give satisfactory results.

Baths compounded in accordance with the present invention are in fact as in theory relatively insensitive to changes in the time and temperature of processing, and full use can be made of this property in practical work, since immersion of gelatine emulsions in the new baths for periods as long as ten times the time required for complete fixation, at temperatures up to degrees F., causes no harmful effect. The inherent compensation of the effect of temperature on activity is such that the solutions may be used at any temperature within the range from 60 degrees to 85 degrees F., using any processing time adequate for complete fixation, with less increase of gamma and density with rising temperature than would be encountered in constant time commercial photographic processing with separate developing and fixing baths over the range from 65 to 75 degrees F.

It is a further advantage of baths compounded in accordance with this invention that the grain of the image produced is finer than is obtained with any heretofore described combined developer and fixer of comparable activity. Heretofore, equivalent activity has been obtained by higher alkalinity, a condition conducive to clumping of the silver particles.

A still further advantage of baths made up in accordance with the present invention is that photographic materials that are to be processed in them may be used at high effective emulsion speeds. In order to obtain comparably high effective emulsion speeds by the methods of the prior art it is necessary to employ developing baths which either give images of coarser grain or require much longer developing time.

In compounding a solution for combined developing and fixing, especially one in which the concentration of the fixing agent is high enough to give complete fixing action in a few minutes, it is essential to employ as one of the constituents a developing agent that is able to in itiate development of latent image centers in a very short period of time. If this immediate initiation of development is not accomplished, many of these latent image centers are destroyed within a few seconds, or even fractions of a second, by the action of the fixing agent. Once development of the latent image centers has been started it is possible to build upon them a silver deposit of higher density, even in the presence of the fixing agent. To promote thi density building process it is advantageous to employ one or more additional developing agents of types which do not possess the power of'rapid initiation of development but which have the property of carrying on the action at a rapid rate once it has been started.

In the formulas of the prior art, almost without exception, the agent used to initiate development has'bee'n monomethyl para-aminophenol sulfate, commonly known as metol. With this agent, however, in order to secure activity high enough to avoid substantial loss of film speed, it is necessary either to raise the alkalinity of the bath to a pH of 11.0 or higher or to carry outthe processing at a temperature substantially highcr'than the commonly accepted optimum temperature of 68 degrees F.

In formulas of the second class of theprior art, in which metol is used in solutions of moderate alkalinity and operated at or near 68 degreesF., it is necessary to limit the amount of fixing agent. The fixing rate must be adjusted to permit substantially complete initiation of development before fixing has proceeded to any considerable extent. ln order to satisfy this condition in formulas of moderate alkalinity in the prior art it has always been found necessary to reduce the concentration of the fixing agent to such a low value that exhaustion of the bath is brought about by exhaustion of the fixing agent while ample amounts of the developing agents are still present. For this reason baths of moderate alkalinity using metol as the initiating agent are not economical to use.

According to the present invention diaminophenol hydrochloride, commonly known as amidol, is used as the induction developing agent, in combination with one or more of the dihydroxy-benzenes. an alkali, a fixingagent, and an inorganic reducing agent, usually sodium sulfite, and preferably with the further additions of a density building organic developing agent having low fogging characteristics and an anti-fogging agent.

Heretofore amidol has not been used in fonnulas requiring good keeping qualities. All published formulas using this agent recommend mixing the bath immediately before use and discarding the used solution. None of 'these published formulas intended for practical use con tains an alkali for the reason that in alkaline solutions, even with large quantities of sodium sulfite, amidol deteriorates very rapidly. It is more usual to add to the solution either sodium bisulfite or one of the metabisulfites in order to neutralize even the slight alkalinity of the sodium sulfite, so that the bath is used in a neutral or even slightly acid condition.

We have discovered that by adding to the solution containing amidol and sodium sulfite an amount of any one of the three dihydroxy-benzenes, that is, of pyrocatechol, resorcinol, or hydroquinone, or of any combination of them, equal to 20 percent or more of the weight of amidol present, this tendency to rapid deterioration is so far overcome that even in alkaline solution the mixture has excellent keeping qualities. The preservative action does not depend on any exact proportioning of the dihydroxybenzene to the amidol. In our working formulas we have adopted the ratio of one part by weight of dihydroxybenzene to three parts of amidol because we have found that this amount is sufiicient to maintain substantially the full activity of the solution even after it has been exposed to the air in a shallow tray for as long as 24 hours. In a stoppered bottle such a solution retains its activity for many months.

While. pyrocatechol, resorcinol, and hydroquinone perform this function of preserving the amidol equally well, the use of hydroquinone is preferred. Resorcinol is not a developer. Hydroquinone and pyrocatechol function as developers and therefore increase the activity of the bath. .Hydroquinone, however, has almost no deteriorating effect on the. grain size of the image, while pyrocatechol does causeaslight increase in the graininess of the image produced.

By the use of amidol in a solution of moderate alkalinity (pH ranging from 8.0 to 9.5) we obtain at an early stage in the process a low contrast image containing substantially all the detail that has been impressed on the photographic emulsion by the exposure it has received. This image in turn is built up in density and contrast by the selective density building developing agent. For this we may use chlorohydroquinone, dichlorohydroquinone, bromohydroquinone, dibromohydroquinone, pyrocatechol, para-hydroxyphenyl glycin, or any other organic developing agent having similar properties. Many suchagents are described in the literature of pho tographic'research. Of the agents listed para-hydroxyphenylglycin, commonly called simply glycin, is preferred where grain size in the developed image is of importance, although pyrocatechol or the halogen compounds of hydroquinone maybe employed equally well where maximum fineness of grain is not of primary importance.

It'should be noted that the halogen compounds of hydroquinone do not share the property of acting as preservative for the amidol; therefore it is necessary to include hydroquinoneitself or one of the other dihydroxybenzenes in the solution in all cases.

Pyrocatechol, one of the dihydroxy-benzenes, has been included in the list of density building, low fogging agents because its properties are such that it is able to perform this function efiiciently. A distinction must be made between the use of pyrocatechol primarily as a preservative for the amidol and its use also as the density building agent. When a weight of pyrocatechol equal to between'20 and 33 percent of the Weight of the amidol is incorporated in the bath it performs the amidol preservative function and also takes part in the developing action, but not to a sufficient extent to produce desirably high image densities. When it is to be used as the principal density building agent it is necessary to use a substantially larger amount, in the range from 75 to percent of the weight of the amidol present. It is also possible to use a similar amount of pyrocatechol in comj H y as.

bination with amidol and the normal preservative amount of hydroquinone or resorcinol, but these combinations present no particular advantage over baths containing only amidol and pyrocatechol.

Sodium carbonate is a suitable alkali for use in baths embodying our invention, especially when sodium thiosulfate is used as the fixing agent. A formula employing these agents is given as the first example in a later part of this disclosure. It has been found, however, that the combination of sodium hydroxide as the alkali and ammonium thiosulfate as the fixing agent is exceptionally advantageous in the preparation of combined developing and fixing baths according to our invention, and this combination is disclosed in greater detail and claimed in the co-pending application of Goldhammer, Ser. No. 410,427, filed concurrently with this application. Formulas 2, 3, 4, 5, and 6, given later as examples, embody both our present invention and the invention of Goldhammer.

Other fixing agents, such as potassium or calcium thiosulfate, sodium or potassium thiocyanate, or sodium or potassium cyanide may be used, but none of these offers any practical advantage over sodium thiosulfate or ammonium thiosulfate.

As an anti-fogging agent we may use either an organic anti-foggant, such as benzotriazole r 6-nitrobenzimidazole nitrate, or an alkali metal bromide. The organic agents are preferred for applications in which it is desirable to be able to process a maximum area of emulsion with a given volume of solution. Where cost of the bath per unit volume is of more importance an alkali metal bromide, usually potassium bromide, is to be preferred.

Sodium sulfite is used in the normal manner as a preservative for the developing agents in compounding baths in accordance with this invention.

The concentrations of the various ingredients may be varied in the generally known manner within wide limits in order to produce gammas ranging from as low as 0.3 to as high as 1.4 to suit the applications. For example, variable density sound track negatives are commonly developed to gammas between 0.3 and 0.5: motion picture negatives are developed to a gamma of approximately 0.65; miniature still camera negatives to gammas of 0.7 to 0.9, ordinary roll films, cut films, and plates to gammas in the range from 0.8 to 1.0; and aerial camera films, X-ray films and X-ray plates to gammas of 1.2 or higher. As in conventional processing, the inherent characteristics of the photographic film or plate partially determine the gamma obtained with any given formula.

The following table lists the preferred ingredients and shows the ranges of concentrations within which useful results are obtained:

In applying the above table it should be understood that when the amount of amidol is increased above 7.5 grams per liter it is desirable to use more than 1.5 grams of hydroquinone so as to keep the concentration of hydroquinone equal to between percent and 33% percent of the concentration of the amidol. Further, it should be understood that with any concentration of sodium hydroxide it is desirable to use enough ammonium thiosulfate to keep the pH not higher than 9.5. Since ammonium thiosulfate is an acid salt it exerts a buffering action which keeps the pH values much lower than they would be without it. This relationship is discussed in detail in the co-pending application of Goldhammer previously referred to.

In the above table pyrocatechol may be substituted for hydroquinone in equal quantities with negligible change in sensitometric results. Resorcinol may be substituted for the hydroquinone in equal quantities with a slight reduction in the gamma and density obtained.

Pyrocatechol, chlorohydroquinone, dichlorohydroquinone, bromohydroquinone, or dibromohydroquinone may be substituted for the glycin in equal amounts provided enough sodium hydroxide or other alkali is added to raise the pH by an amount not more than 1.0 above the pH of the formulation using glycin.

The following examples are formulas specifically designed in accordance with the invention for the applications stated.

N0. 1.A formula using sodium carbonate and sodium thiosulfate, suitable for processing portrait negatives on high speed or medium speed films or plates:

Water (120 F.) cc 700 Sodium sulfite (anhydrous) g 50 Amidol g 15 Hydroquinone g 5 Glycin g 10 6-nitrobenzimidazole nitrate g 0.4 Sodium carbonate (monohydrated) g 50 Sodium thiosulfate (crystal) g 100 Water to make 1000 cc.

pH=9.5. Time, 6 minutes at 68 F. Gamma on high speed films 0.75, on medium speed films 0.85 to 0.90.

No. 2.--Application-processing of high and medium speed panchromatic and orthochromatic roll films:

Water (120 F.) cc 750 Sodium sulfite (anhydrous) g 50 Amidol g 15 Hydroquinone g 5 Glycin g 10 6-nitrobenzimidazole nitrate, 0.5

percent solution cc 80 Potassium bromide g 5 Sodium hydroxide g 20 Ammonium thiosulfate g 50 Water to make 1000 cc.

pH=8.7. Time, 3 minutes at 68 F. Gamma on high speed panchromatic films, 0.85.

No. 3.A formula using pyrocatechol for the same application as No. 2:

Water (120 F.) cc 750 Sodium sulfite (anhydrous) g 50 Amidol g- 15 Pyrocatechol g 15 Potassium bromide g 5 Sodium hydroxide g 25 Ammonium thiosulfate g 50 Water to make 1000 cc.

pH=9.3. Time, 3 minutes at 68 F. Gamma on high speed panchromatic films 0.85.

No. 4.-Application--processing of high speed panchromatic motion picture negative films:

speed panchromatic negative motion picture film 0.60.

No. 5.A formula using only amidol and hydroquinone, suitable for panchromatic motion picture negative films:

\Vater (120 F.) M cc 750 Sodium sulfitc (anhydrous) g 40 Amidol ..g- 15 Hydroquinone g 6-nitrobenzimidazole nitrate -g 0.4 Sodium hydroxide g. 10 Ammonium thiosulfate g 50 Water to make 1000 cc.

pH=9.0. Time, 3 minutes at 68 F. Gamma 0.65

No. 6.-A formula for applications requiring higher contrast:

Water (120 F.) cc 750 Sodium sulfite g 30 Amidol g Hy'droquinone g 5 Glycin g 10 6-nitrobenzimidazole nitrate (5% solution) ml 80 Sodium hydroxide g 15 Ammonium thiosulfate g 25 Water to make 1000 cc.

pH=9.5. Time, 6 minutes at 68 F. Gamma on high speed panchromatic films 1.0, on medium speed panchromatic films 1.2 to 1.4.

We have found that the ingredients of any of the above formulas, with the exception of the water, may be mixed together in dry formin the proportions stated, and that these mixtures have excellent keeping qualities as long as they are kept in airtight containers. Combined developing and fixing baths may then be prepared conveniently at any time they are needed by dissolving the appropriate mixture of dry chemicals'in the proper volume of water. I

Research over many years in the field of developing agents has shown that there are two chemical groups, or radicals. which when attached to a benzene ring confer the power of developing photographic latent :irnages (except in certain well known combinations which are inactive). These activity conferringgroups are the hydroxyl (OH) and amino (-NH2) groups. We must include also the various substituted amino groups. in which one or both of the hydrogen atoms .is or are replaced by an organic radical such as the methyl group (-CHs) the ethyl group (-C2H5) or by agroup containing another benzene ring of which oneo'f the carbon atoms is attached to the nitrogen atom of the amino group in place of the hydrogen atom. As far as the developing activity conferred by the group is concerned these substituted amino groups have essentially the same effect as the amino (NH2) group itself.

Amidol belongs to a class of developing agents in which more than two of these activity-conferring groups are attached to a single benzene ring. This includes'agents which have one hydroxyl and two amino groups (as does amidol itself) as well as others in which there are three amino groups and some in which there are two hydroxyl and two amino groups. In addition to their chemical structure these agents are characterizedby the fact that they develop in acid solutions as well as (in neutral or alkaline solutions, whereas the great majority of developing agents are inactive in acid solution.

Amidol is theohlym'emberof this class that is manufactur'ed in quantity and commercially available at the present time. Theliterature, however, records numerous other exam'plesbf this class of developing agents which have been "found to have characteristics similar to those of amidol. For convenience these may be referred to as developing agents of the amidol type. Specific examples are the following compounds:

(1)11 UNHQ NH: (Amidol) 2,4 dlamlnophenol 2,4 diamlnoresorcinol CH3- -NH2 (D. R. P. 74,842)

G-methyl 2,4, diamlnophenol -NHz (D. R. P. 74,842) CH2 fi-methyl 2,4, dl'ain'inophenol 441mino banethyl 2-methylamlnophenol NH NH-OH:

G-amino-4-methy1-2-methylamino-phenol (Mees) 1,2,4 trlaminobenzene NHa NHQ

-rnethyl 1,2,4 trlamino benzene 4 hydroxy 2'4 diaminodiphenylamine 4 2'4 triaminodiphenylamlne (D. R. P. 60,174) NH:

1,3 diamino 4,6 dihydroxybenzene It is obvious that any of these developing agents of the amidol type might be substituted for amidol in making up baths for combined developing and fixing in accordance with the present invention. For example, triaminobenzene-dihydrochloride when substituted for amidol in equal quantity in the formula given above as Example 2, gives a bath having substantially the same properties as the one using amidol. We regard all such substitutions as coming within the scope of the invention.

What is claimed is:

1. In a chemical composition of increased activity and having in aqueous solution a pH value not in excess of 9.5 and adapted for combined developing and fixing of silver halide photographic emulsions, the combination of a developing agent selected from the group consisting of 2,4 diaminophenol (amidol), 2,4 diaminoresorcinol, 6- methyl-2,4-diaminophenol, S-methyl 2,4-diaminophenol, 4-amino 6 methyl 2 methylamino-phenol, 6-amino-4- methyl-Z-methylamino-phenol, S-dimethylamino-Z-methylamino-phenol, 1,2,4-triaminobenzene, S-methyl 1,2,4-triaminobenzene, 4-hydroxy 2,4' diaminodiphenylamine, 4:2',4 triaminodiphenylamine, and 1,3-diamino 4,6-dihydroxybenzene; a dihydroxybenzene selected from the group consisting of pyrocatechol, resorcinol and hydroquinone; the ratio of the dihydroxybenzene to the developing agent being in the range from 7.5% to 200% by weight, an alkali, and a fixing agent selected from the group consisting of thiosulfates and cyanides.

2. In a chemical composition of increased activity and having in aqueous solution a pH value not in excess of 9.5 and adapted for combined developing and fixing of silver halide photographic emulsions, the combination of an inorganic reducing agent, a developing agent from the group consisting of 2,4-diaminophenol (amidol), 2,4-diaminoresorcinol, 6-methyl 2,4-diaminophenol, S-methyl- 2,4 diaminophenol, 4-amino-6-methyl 2 methylaminophenol, 6-amino-4-methyl 2 methylamino-phenol, S-dimethylamino-2-methylamino-phenol, 1,2,4 triaminobenzene, S-methyl 1,2,4 triaminobenzene, 4-hydroxy:2',4- diaminodiphenylamine, 4:2,4' triaminodiphenylamine, and l,3-diamino-4,6-dihydroxybenzene; a second developing agent from the group consisting of chlorohydroquinone, dilchlorohydroquinone, and para-hydroxy phenyl glycin; at least one of the dihydroxybenzenes selected from the group consisting of pyrocatechol, resorcinol and hydroquinone; the ratio of the dihydroxybenzene to the developing agent lying in the range from 7.5 to 200% by weight; an alkali, a thiosulfate fixing agent, and an antifoggant.

3. In a chemical composition of increased activity and having in aqueous solution a pH value not in excess of 9.5 and adapted for combined developing and fixing of silver halide photographic emulsions, the combination of amidol, at least one of the dihydroxybenzenes selected from the group consisting of pyrocatechol, resorcinol and hydroquinone; the ratio of the dihydroxybenzene to the amidol lying in the range from 7.5% to 200% by weight, an alkali, and a thiosulfate fixing agent.

4. In a chemical composition of increased activity and having in aqueous solution a pH value not in excess of 9.5 and adapted for combined developing and fixing of silver halide photographic emulsions, the combination of sodium sulfite, amidol, a second developing agent selected from the group consisting of chlorohydroquinone, dichlorohydroquinone, bromohydroquinone, dibromohydroquinone, and para-hydroxyphenyl glycin; at least one of the dihydroxybenzenes selected from the group consisting of pyrocatechol, resorcinol and hydroquinone; the ratio of the dihydroxybenzene to the amidol lying in the range from 7.5 to 200% by weight; an alkali, a thiosulfate fixing agent, and an anti-foggant.

5. In a chemical composition of increased activity and having in aqueous solution a pH value not in excess of 9.5 and adapted for combined developing and fixing of silver halide photographic emulsions, the combination of amidol, hydroquinone, the hydroquinone to amidol ratio lying in the range from 7.5% to 200% by weight, an alkali, and a thiosulfate fixing agent.

6. An aqueous solution having a pH value not in excess of 9.5 and adapted for the combined developing and fixing of silver halide photographic emulsions containing the ingredients listed in the following table in relative proportions within the limits stated:

Water liter 1 Sodium sulfite (anhydrous) grams 30.0 to 50.0 Amidol do 5.0 to 20.0 Glycin do 5.0 to 10.0 Hydroquinone do 1.5 to 10.0 6-nitrobenzimidazole nitrate do 0.0 to 0.4

together with an alkali and a thiosulfate fixing agent.

7. An aqueous solution having a pH value not in excess of 9.5 and adapted for the combined developing and fixing of silver halide photographic emulsions containing the ingredients listed in the following table in relative proportions within the limits stated:

Water liter 1 Sodium sulfite (anhydrous) grarns 30.0 to 50.0 Amidol do 5 .0 to 20.0 Glycin do 5.0 to 10.0 Hydroquinone do 1.5 to 10.0 Potassium bromide do 0.0 to 10.0

together with an alkali and a thiosulfate fixing agent.

8. A dry mixture adapted to be dissolved in water to produce a solution having a pH value not in excess of 9.5 for the combined developing and fixing of silver halide photographic emulsions containing the ingredients listed in the following table in the relative proportions within the limits stated:

Parts by weight Sodium sulfite (anhydrous) 30.0 to 50.0 Amidol .0 to 20.0 Glycin 5.0 to 10.0 Hydroquinone 1.5 to 10.0

6-nitrobenzimidazole nitrate 0.0 to 0.4

together withan alkali and a thiosulfate fixing agent.

9. A dry mixtureadapted to be dissolvedin'water to produce a solution'having a pH value notin excess of 9.5 for-the combined developing and fixing of silver halide photographic emulsionscontaining the ingredients listed in the following table in the .relative proportions within the limits stated:

Parts by weight Sodium sulfite anhydrous) 30.0 to 50.0 Amidol 5 .0 to 20.0 Glycin 5.0 to 10.0 Hydroquinone 1.5 to 10.0

Potassium bromide 0.0 to 10.0

together with an alkali and a-thiosulfate fixing agent.

10. An aqueous solution having a pH of 9.5 and adapted for combined developing and fixing of silver halide photographic emulsions containing the ingredients listed in the following formula in substantially the relative proportions stated:

12 11. A dry mixture adapted to be dissolved in water to produce a solution having a pH of 9.5 and for combined developing and fixing of silver halide photographic emulsions, containing the following ingredients in substantially the proportions stated:

Parts by weight Sodium sulfite (anhydrous) Amidol 15 Glycin 10 Hydroquinone 5 6-nitrobenzimidazole nitrate 0.4 Sodium carbonate (monohydrated) 50 Sodium thiosulfate (crystal) n 12. The chemical composition according to claim 3 in which the dihydroxybenzene is pyrocatcchol and the pyrocatechol to amidol ratio lies in the range from 20% to 33 /3 by weight.

13. The chemical composition according to claim 3 in which the dihydroxybenzene is hydroquinone and the .hydroquinone to amidol ratio lies in the range of from 20% to 33%% by weight.

14. The chemicalcomposition according to claim 3 in which the dihydroxybenzene is hydroquinone, the alkali is sodium carbonate, and the fixing agent is sodium thiosulfate.

References Cited in the file of this patent UNITED STATES PATENTS 7 2,333,766 Crabtree Nov. 9, 1943 2,366,496 Dawson Jan. 2, 1945 2,397,676 Lyon Apr. 2, 1946 2,543,181 Land Feb. 27, 1951 FOREIGN PATENTS 299,751 Great Britain Oct. 29, 1928 OTHER REFERENCES Amidol Formulae, British Journal of Photography, Oct. 3, 1924, page 598. 

1. IN A CHEMICAL COMPOSITION OF INCREASED ACTIVITY AND HAVING IN AQUEOUS SOLUTION A PH VALUE NOT IN EXCESS OF 9.5 AND ADAPTED FOR COMBINED DEVELOPING A FIXING OF SILVER HALIDE PHOTOGRAPHIC EMULSIONS, THE COMBINATION OF A DEVELOPING AGENT SELECTED FROM THE GROUP CONSISTING OF 2,4 - DIAMINOPHENOL (AMIDOL), 2,4 - DIAMINORESORCINOL, 6METHYL-2,4-DIAMINOPHENOL, 5-METHYL - 2,4-DIAMINOPHENOL, 4-AMINO - 6 - METHYL - 2 - METHYLAMINO-PHENOL, 6-AMINO-4METHYL-2-METHYLAMINO-PHENOL, 5-DIMETHYLAMINO-2-METHYLAMINO-PHENOL, 1,2,4-TRIAMINOBENZENE, 5-METHYL - 1,2,4-TRIAMINOBENZENE, 4-HYDROXY :2'',4'' - DIAMINODIPHENYLAMINE, 4:2'',4'' - TRIAMINODIPHENYLAMINE, AND 1,3-DIAMINO-4,6-DIHYDROXYBENZENE; A DIHYDROXYBENZENE SELECTED FROM THE GROUP CONSISTING OF PYROCATECHOL, RESORCINOL AND HYDROQUIINONE; THE RATIO OF THE DIHYDROXYBENZENE TO THE DEVELOPING AGENT BEING IN THE RANGE FROM 7.5% TO 200% BY AN ALKALI, AN ALKALI, AND A FIXING AGENT SELECTED FROM THE GROUP CONSISTING OF THIOSULFATES AND CYANIDES. 